The present invention relates to a circuit for activating one of a plurality of circuits in response to momentary actuation of a selection switch associated therewith and, more particularly, to such a circuit in which activation of a circuit is automatically terminated both in response to actuation of its associated selection switch or actuation of the selection switch of any other of the plurality of selectable circuits.
In numerous applications it is desired to selectively activate any one, but only one, of a plurality of selectable circuits. For example, in an electronic organ, a plurality of voicing circuits are often provided, each one of which alters the played tones differently to simulate the sounds of different musical instruments, such as a guitar, trumpet, etc. In such a case, it is desirable to enable the organist to easily change his selection from one voicing circuit to another and to terminate any one selection without choosing another so that none of the voicing circuits are activated.
Mechanical switch assemblies are known having a mutually exclusive interlock feature which automatically causes release of any actuated switch upon actuation of any other selector switch of the assembly. Unfortunately, such switch assemblies are relatively expensive and are prone to failure due to mechanical wear, fatigue, etc. Furthermore, a separate actuator is often required to release an actuated switch by means other than making another selection.
Electronic circuits analogous to the mechanical switch assemblies noted above are known which use a separate electronic memory for each switch to maintain actuation of the circuit associated therewith after release of the selector switch. This enables the use of relatively inexpensive momentary contact switches, but the resultant reduction in cost is partially offset by the cost of multiple memories.
Circuits of this type have other disadvantageous qualities which detract from their utility. Often steering networks and other circuitry having a high component count are required to control the plurality of memories in accordance with switch actuation which further adds to complexity and cost. Further, such circuits are also disadvantageously susceptible to switch contact bounce resulting in a single operator actuation of a switch successively setting and resetting in succession a memory associated therewith. Moreover, known circuits employing momentary contact switches and individual memories require the use of an additional circuit associated with a cancelling switch to terminate activation of all multiple circuits. An example of such a selector circuit is shown in U.S. Pat. No. 3,660,683 of Wangard issued May 2, 1972, to Walter E. Heller & Company.